How to Fix Ford 4.6 Coolant Leaks

It’s been nearly two years since we last wrote about Project Panther, our 2003 Ford Crown Victoria. Rest assured, it’s still here and running stronger than ever with Trick Flow’s top-end kit and Stainless Works exhaust. After this much time and about 15,000 miles since we rebuilt the engine, there have been no issues, zero oil consumption and no leaks of any kind, until late last year when a small puddle of coolant would appear underneath the car after sitting for more than two days without being driven.

Fluid leaks can be hard to trace. A puddle on the ground underneath the back of the engine can actually originate from a source near the front of the engine. It takes some investigative work to find the exact cause of a leak, and here’s how we did that and ultimately solved the problem.

2/9We originally suspected a bad thermostat-housing gasket and replaced it (it’s actually just an O-ring), but that didn’t stop the leak. The logical remaining alternative was a faulty intake-manifold gasket. Out of curiosity, we stuffed shop towels along the front and rear edges of the manifold to see exactly where the leak was coming from. In the morning, the only wet towels were at the rear of the intake. Removing the intake manifold isn’t difficult, but it did require removing the hood. That way, we could remove the whole windshield wiper assembly, which allowed much easier access to all the intake manifold fasteners.

3/9The only special tool required is this fuel-line disconnect tool. No big deal, they are sold at all the major auto-parts retailers. Just push the tool into the fuel fitting to disconnect the fuel lines. When reinstalling them, the lines just push together.

4/9Removing the intake is very straightforward. Upon inspection, we discovered the leak emanated from the manifold itself, not the gasket as we had suspected. The crack in the manifold extends from the sealing surface to deep inside the coolant passage. This is actually just a coolant block-off. The corresponding coolant passage on the passenger-side cylinder head is the return path from the heater core.

5/9We toyed with the notion of packing the crack full of RTV and reusing the manifold but ultimately decided to replace it instead. With more than 175,000 miles on the engine, this was bound to happen again. Early Non-Power Improved manifolds had problems with coolant leaking at the crossover at the front of the manifold, since the crossover was plastic on those engines. Ford changed to an aluminum crossover on Power Improved engines to fix this problem, but judging by the residue on our manifold, coolant was seeping here, too.

6/9Junkyards across the country are littered with SOHC 4.6-powered Fords, so a replacement manifold should just be a short trip away. Be sure to check the donor car’s odometer, though. We’ve seen taxis in our local junkyards with mid-300,000 miles racked up on them. You may want to pass on the manifold from one of these cars.

7/9We’ve discussed it before in prior articles, but be aware of the intake-port differences between the early 4.6 heads and later Power Improved heads.

ModularHeadShop.com/piintakeswap.aspx for all the details. ">
8/9You can actually put a PI manifold on NPI heads, but there are a couple modifications you need to make, and they are described in great detail on Modular Head Shop’s website. Go to <a href="http://www.ModularHeadShop.com/piintakeswap.aspx" target="_blank" rel="nofollow">ModularHeadShop.com/piintakeswap.aspx</a> for all the details.

9/9The beauty of using FRPP’s manifold versus an aftermarket one is that everything bolts back on it in exactly the right place. Aftermarket manifolds are available, like this Victor Jr. from Edelbrock, but it was just a bit too tall to fit under our car’s hood. We dropped on new intake gaskets and transferred all of the brackets and components from the old manifold. The car was running within an hour, and it has been leak-free since then.